Spondyloarthritis (SpA) patients have two distinct clusters. In principal coordinates analysis (A) each subject is a separate dot; the closer two subjects are in space, the more similar their sequence data. Enthesitis-related arthritis (ERA) subjects are shown in blue, controls in red. The asterisks over eight of the subjects indicate subjects identified as well with the pvclust bootstrap analysis (B). The same eight subjects are present in the identified cluster.